1. Field of the Invention
The present invention relates to a screen device for sorting fiber suspensions with a multitude of substantially parallel aligned rods. Between the parallel rods are sorting slots or sorting slits which are fixed in the supporting elements and cover elements.
2. Discussion of Background Information
It is known to use this type of device for sorting fiber suspensions. The fibers contained in the suspension are to pass through the screen, while undesired solid components are rejected at the slot (or slit) and removed from the screen device. Another conceivable use for the device is the separation of varying fiber components. Due to the fact that the openings are substantially longitudinal in shape, i.e., slots or slits, the fibrous particles pass through these slots more easily than cubic particles, even if both particles have a similar order of magnitude. This type of sorting technology, therefore, has an excellent capability of removing non-fibrous interfering substances from the fiber suspension. This, however, requires dimensional stability and a high precision of the slot shape on the entire screen surface.
In many cases, such screen devices are subject to severe wear and thus need replacing.
A method for producing rod wire or screen or sieve baskets is shown in DE 39 27 748 A1, wherein the sectional rods are clamped by an elastic deformation of the supporting rings that include recesses for holding the rods. Sectional rods, which are particularly suitable for this type of production method, are used. This method allowed one to considerably reduce the production costs, however, when using this type of screen basket, certain restrictions could not be ruled out, especially when subjected to intensive mechanical loads.
Screens or screen elements with good stability and excellent surface quality may also be produced according to a method described in DE 42 14 061 A1. There, the rod-shaped profiles are fixed by using a high-temperature soldering method. The result is excellent, but the process is burdensome and expensive.
EP 0 724 037 A2 describes slot-shaped screen or sieve baskets that are designed with sortings slots formed between parallel rods. The rods pass through supporting rings which hold the rods at the required lateral distance. The supporting rings are connected by spacers, which ensure that the shape of the screen basket is maintained, even if the rods that define the sorting slot are removed. This type of design, however, does not produce adequate stability in all cases.
EP 0 719 890 A2 describes another rod wire or screen device. There, the rods are designed to increase in thickness so that they maintain the distance necessary for forming the slot. Even if the wires produced by this method offer the advantage of easy dismantling, the production of these rods is relatively costly. Further, it is difficult to guarantee adequate stability with this type of wire.